JPH0474804B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a non-foamed printed circuit board with excellent conduction reliability that is composed of conductive magnetic particles (hereinafter referred to as "magnetic particles") and insulating polymer elastic bodies (hereinafter referred to as "elastic body"). This invention relates to an anisotropically conductive rubber sheet for inspection. Microscopic mechanical parts are frequently used in the electronics industry, and as packaging density increases, the method of mounting these onto substrates has become an important issue. In other words, most of the mounting methods used up until now have been by soldering, but since electronic components such as semiconductor devices are generally sensitive to heat, it is undesirable to expose them to high temperatures, even temporarily. It has been difficult to attach components to the board without damaging them. Furthermore, in mounting the printed circuit board onto the main body, mechanical interlocking has often been mainly used until now, but this has resulted in poor contact due to wear and vibration of the contact portions. Recently, anisotropically conductive rubber sheets (for example, JP-A-Sho
49-51593, JP 51-93393, JP 53-53796, and JP 52-65892) as a connector,
It has become clear that the above problems can be improved, but for example, when mounting parts at the same time as assembly using the space inside the case, when mounting with particular emphasis on vibration isolation, and when using for printed circuit board inspection. There have been cases where the performance has not always been satisfactory, such as when wearing devices that require contact over a large area. As a result of intensive research in order to solve the above problems, the present inventors found that the characteristics of the anisotropically conductive rubber sheet required for the above-mentioned mounting are more important than the resolution and sensitivity of the surface (contact surface). ) The present invention was completed based on the knowledge that reliable contact can be achieved with a relatively small clamping pressure (pressing force) even if the surface has some irregularities, that is, continuity reliability is important. That is, the present invention mainly consists of conductive magnetic particles with a particle size of 10 to 100 μm and an insulating polymer elastic body,
The hardness (obtained according to JIS AHs) obtained by applying magnetic field treatment to crosslinking an uncured composite containing a crosslinking agent is 25 to 45, and the thickness is 10mm.
The present invention provides a non-foamed anisotropically conductive rubber sheet, particularly an anisotropically conductive rubber sheet used for inspecting printed circuit boards, which is characterized by the following characteristics. Note that the anisotropically conductive rubber sheet in the present invention is a rubber sheet that is electrically conductive only in the thickness direction. Examples of magnetic particles that can be used in the present invention include particles made of iron, nickel, cobalt, or alloys thereof, and particles plated with silver or gold. Particles having the following properties are economically preferable. The particle size of the magnetic particles is 10 to 100 μm, and is selected depending on the thickness of the anisotropically conductive rubber sheet. The elastic bodies used in the present invention include polybutadiene, natural rubber, polyisoprene,
SBR, NBR, EPDM, EPM, urethane rubber,
Examples include polyester rubber, chloroprene rubber, epichlorohydrin rubber, and silicone rubber. The uncured composite used in the present invention is a mixture of magnetic particles and an elastic material, a crosslinking agent, preferably a mono-, di-, or trial-alkyl titanate as described below, and, in some cases, further hardness. The composite is well mixed by mechanical means, such as a twin screw kneader, with the addition of a modifier. The preferred amount of magnetic particles added is 3 to 25% by volume based on the uncured composite. In addition, mono-alkyl titanate is represented by the following general formula, (RO)-Ti(OR ₂ ) ₃ or (RO)-Ti(OXR ₂ ) ₃ (where R is an alkyl group with 1 to 4 carbon atoms, R ₁ is a vinyl group, and 6 or more carbon atoms) represents an alkyl group, an aralkyl group or an aryl group having 6 or more carbon atoms, R ₂ is an alkyl group having 6 or more carbon atoms,
Represents an aralkyl group or aryl group having 6 or more carbon atoms, and X is

[expression] or

[Formula] is shown. ) Di-alkyl titanates and trialkyl titanates are represented by the following general formula. (RO)nTi( ^OR1 ) _4-o (n is 2 or 3) (Here, R is an alkyl group having 6 or more carbon atoms.) Preferred addition amount of mono-, di- or tri-alkyl titanate is 0.05 to 2% by volume based on the uncured composite. The addition of mono-, di-, or trialkyl titanates facilitates mixing and molding of the uncured composite and improves the mechanical properties (durability) and electrical properties of the anisotropically conductive rubber sheet. performance will be improved. The crosslinking agent used in the present invention is a commonly used crosslinking agent for rubber. In addition, as hardness modifiers, RTV thinner (manufactured by Shin-Etsu Chemical Co., Ltd.), 1204 thinner (manufactured by Shin-Etsu Chemical Co., Ltd.)
Examples include. The anisotropically conductive rubber sheet of the present invention is obtained by subjecting an uncured composite mainly composed of magnetic particles and an elastic body to a magnetic field treatment and crosslinking it.
The hardness of the obtained rubber sheet must be between 25 and 45. If the hardness is less than 25, for example, when the rubber sheet is used as a connector, durability will be extremely deteriorated due to repeated deformation, and mechanical strength will be reduced, making it impossible to maintain long-term contact. On the other hand, if the hardness exceeds 45, for example, when the rubber sheet is used as a connector, the clamping pressure required to maintain normal conduction will be high, and contact will only be possible in areas where flatness is maintained fairly strictly. . In the present invention, the time for applying the magnetic field and the intensity of the magnetic field may be such that the magnetic particles in the uniformly dispersed elastic body are aligned by the magnetic field and are sufficiently stabilized. For example, in the case of RTV type silicone rubber,
It is sufficient to apply a magnetic field strength of 2000 Gauss or more for about 10 to 60 minutes. In the present invention, crosslinking of the uncured composite is generally carried out by subjecting the uncured composite to magnetic field treatment and then increasing the temperature in that state. It may also be crosslinked. The thickness of the anisotropically conductive rubber sheet of the present invention is determined from a practical standpoint, but it needs to be 10 mm or less, preferably 0.5 to 10 mm, more preferably 1 to 5 mm. The uncured composite used in the present invention is filled with colloidal silica, silica airgel, kaolin, mica, talc, wollastonite, calcium silicate, aluminum silicate, chalk, calcium carbonate, iron oxide, alumina, etc. Although it is possible to contain up to 30 volume fraction (%) of the agent, if a large amount is blended, the compression set and electrical properties will deteriorate, making it impractical. However, from the viewpoint of preventing rearrangement of the magnetic particles after crosslinking, it is preferable to mix an appropriate amount of filler. Additionally, additives such as process oil can be added to the uncured composite as necessary. The anisotropically conductive rubber sheet of the present invention has low hardness, so the clamping pressure is low, and it not only has excellent continuity reliability, but also extremely excellent current capacity, insulation properties, mechanical properties, etc. Therefore, the non-foamed anisotropically conductive rubber sheet of the present invention is most suitable for use in inspecting printed circuit boards used over a large area. The present invention will be described below with reference to examples, but the present invention is not limited to these examples unless it goes beyond the gist of the present invention. Example 1, Comparative Example 1 Additive silicone rubber (manufactured by Shin-Etsu Chemical Co., Ltd.,
KE1206RTV), 15 volume fraction (%) of nickel particles (manufactured by Sielitz, hydrogen pressurized nickel, particle size approximately 100 μm) were added, and predetermined amounts of crosslinking agent and hardness modifier (manufactured by Shin-Etsu Chemical Co., Ltd.) were added. , RTV thinner), etc. using a twin-screw kneader in a vacuum for 60 minutes, and then poured into a magnetic mold body 5 of a predetermined thickness as shown in FIG. After sufficiently bubbling under vacuum, the mold was covered with a magnetic mold upper plate 4, placed between electromagnets 1 via a heater 3, and a parallel magnetic field of approximately 4000 Gauss was applied at room temperature for 20 minutes. Processed. Next, the temperature was raised to about 75°C and crosslinking was carried out for 2 hours to obtain a rubber sheet with a thickness of 2 mm. This rubber sheet was conductive only in the thickness direction of the sheet, and no conductivity was observed in the surface direction of the sheet. Further, Table 1 shows the results of the following conductivity reliability test for this rubber sheet. Table 1 shows that the anisotropically conductive rubber sheet of the present invention has excellent continuity reliability. <Continuity Reliability Test> In Fig. 2, the rubber sheet 7 as a sample is sandwiched between the upper electrode printed circuit board 8 and the lower electrode printed circuit board 10, and the upper electrode holding plate 9 is pressed in the direction of arrow A ( (by changing the clamping pressure), it is judged from the resistance value between the opposing electrodes 12, 12' whether or not there is conduction across all the electrodes attached to the substrates 8, 10. In addition, in this test, the resistance value
If it was 100Ω or less, it was considered to be conductive, and if it exceeded 100Ω, it was considered not to be conductive. In addition, "100% conduction of the opposing electrodes" shown in Table 1 means that
This means that there is continuity between all electrodes, and in this test, 60 electrodes were used (electrodes 12
60 pieces and 60 pieces of electrode 12').

【table】

[Table] Example 2, Comparative Example 2 Experiment numbers 1-2, 1-3, 1 in Example 1
Rubber sheets with the same composition as -4, 1-1' and 1-3' and various thicknesses were prepared in the same manner as in Example 1, and the following continuity reliability test was conducted using these rubber sheets. . The results are shown in Table 2. Table 2 shows that the rubber sheet of the present invention has excellent conduction reliability. <Continuity reliability test> As shown in Figure 3, spacers 1 of various thicknesses were tested.
3 was placed between the lower electrode printed circuit board 10 and the lower electrode holding plate 11 to provide a step, and a concavo-convex surface was created on the sample rubber sheet 7, and a continuity reliability test similar to that in Example 1 was conducted. .

【table】

[Table] Example 3 Same composition as Experiment No. 1-3 in Example 1, except that a titanium coupling agent [bis(triethanolamine) diisopropyl titanate] was added to the uncured composite. A rubber sheet was prepared in the same manner as above, and a durability test was conducted. The results are shown in Table 3. The durability test was carried out by repeatedly pressurizing the rubber sheet and determining the number of times of repeated pressurization when the result of the continuity reliability test similar to Example 1 changed from ◎ to △. Ta. From Table 3, it can be seen that the addition of a titanium coupling agent greatly improves the durability.

[Table] Comparative Example 3 Same composition as Experiment No. 1-2 in Example 1, except that 5% by weight of a blowing agent (p,p'-oxybisbenzenesulfonyl hydrazide) was added to the uncured composite. A foamed rubber sheet having a thickness of 5 mm was prepared in the same manner as in Example 1, and a continuity reliability test similar to that in Example 1 was conducted using this foamed rubber sheet. As a result, the clamping pressure was 5 gf/mm ² and the evaluation was poor, and electrical conduction occurred with electrodes other than between the opposing electrodes, and anisotropic conductivity could not be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of an apparatus that applies a magnetic field to an uncured composite, and FIGS. 2 and 3 are diagrams showing a method for testing continuity reliability. 1... Electromagnet, 2... Heating plate, 3... Heater,
4... Mold upper plate, 5... Mold body, 6... Uncured composite, 7... Rubber sheet, 8... Upper electrode printed circuit board, 9... Upper electrode holding plate, 10... Lower electrode Printed circuit board, 11...Lower electrode holding plate, 1
2, 12'...electrode, 13...spacer.

Claims (1)

[Claims] 1 Hardness (JIS required according to AHs)
25 to 45 and a thickness of 10 mm or less, a non-foamed anisotropically conductive rubber sheet for inspecting printed circuit boards.